This invention is concerned with new compounds having one, two or three aldimine groups and one, two or three oxyazolidine groups. Said new compounds are curing agents for polyisocyanates.
Traditionally polyurea polymers and polyurethane polymers respectively are prepared by mixing polyisocyanates with polyamines and polyhydroxy compounds respectively. If polyamines or polyhydroxy compounds are used as curing agent or component of a curing agent, then the mixtures of polyisocyanates and said curing agents are stable only for very short periods, and they have to be used immediately after mixing.
It is furthermore known that oxazolidines like aldimines and ketimines, i.e. condensation products of keto compounds with amines, generally named Schiff bases, do not react or react only very slowly. Polyaldimines, polyketimines and polyoxazolidines are described in the art and furthermore also their use as components of mixtures with polyisocyanates. With regard to this, reference is made to the British Pat. No. 1 064 841 and the German Offenlegungsschrift No. 2 356 213, No. 1 952 091, No. 1 952 092, No. 2 446 438 and No. 2 458 588. Such mixtures are stable for longer periods if humidity is absent. When they are contacted with water or the humidity of the environment there is liberated by the hydrolysis a polyamine which reacts with the polyisocyanate of the mixture forming urea bonds.
Surprisingly, it now has been found that new compounds having one or more aldimine groups and one or more oxazolidine groups if mixed with polyisocyanates result in mixtures having an extremely long shelf life, provided that the access of humidity is prevented. If however said mixtures are contacted with water, the polymerization proceeds very fast resulting in hard or elastic polymers.
The so cured polymers have a good resistance against chemicals and solvents.
It is thus an object of the present invention to provide new compounds having one or more aldimine groups and one or more oxazolidine groups in their molecule.
A further object of the invention is a process for preparing said new compounds.
Another object of the invention is the use of the new compounds as curing agent for organic polyisocyanates.
A further object of the invention are compositions which are curable by the application of water or humidity of the environment and which contain the new compounds of the invention and furthermore a polyisocyanate.